In the course of the ever stricter regulatory provisions for new motor vehicles, in particular also for hybrid vehicles, exhaust-gas aftertreatment devices must be used for the aftertreatment of the exhaust gases produced during the combustion so that the produced emissions are reduced to the limit value prescribed by the regulations.
It is problematic in this context that partially very high temperatures are produced by the exhaust gas, in particular in nonstationary operating points of the combustion engine, so that the exhaust-gas aftertreatment systems situated in the exhaust-gas tract have to be protected from the effects of excessive heat.
German Published Patent Application No. 10 2015 226 216 describes a method and a device for operating a motor vehicle (2) having a hybrid drive, which is made up of a combustion engine (3) and an electric machine (4), both of which are acting on a shared hybrid drive train (1); in order to operate components of an exhaust-gas aftertreatment system (20), the combustion engine (3) is at least intermittently operated in a phase featuring a rich air/fuel mixture or it is operated using an exhaust-gas recirculation in order to lower the exhaust-gas temperature. When a greater load requirement arises for the combustion engine (3) during the phase in which a rich air/fuel mixture is used for the operation, or during the phase when the operation features an exhaust-gas recirculation, the torque (MD_VKM) of the combustion engine (3) is kept constant and the additional torque required on account of the greater load requirement is supplied exclusively by the electric machine (4).